Chemically modified targeting protein and use thereof

ABSTRACT

Provided is a chemically modified targeting protein, a pharmaceutical composition including the chemically modified targeting protein, a conjugate including the chemically modified targeting protein and a drug, and methods for preparing the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 10-2014-0060544 filed on May 20, 2014 in the Korean Intellectual Property Office, the entire disclosure of which is hereby incorporated by reference.

INCORPORATION BY REFERENCE OF ELECTRONICALLY SUBMITTED MATERIALS

Incorporated by reference in its entirety herein is a computer-readable nucleotide/amino acid sequence listing submitted herewith and identified as follows: One 132,726 byte ASCII (Text) file named “720523 ST25.TXT” created May 11, 2015.

BACKGROUND OF THE INVENTION

1. Field

Provided are a chemically modified targeting protein, a pharmaceutical composition for drug delivery including the chemically modified targeting protein, and a conjugate of the chemically modified targeting protein and a drug.

2. Description of the Related Art

Low molecular drugs, in particular low molecular protein drugs, have short half-lives and short administration intervals; thus, if they are cytotoxic and non-specifically uptaken, the cytotoxicity may affect normal tissues.

To solve these problems due to the non-specific uptake, a targeting protein-drug conjugate (e.g., antibody-drug conjugate; ADC), where a targeting protein such as an antibody and a drug are conjugated, has been developed.

However, there are still remained several problems such as decrease in stability due to formation of aggregation between drugs, non-specific uptake due to external exposure of a drug, short half-life in a living body, low intracellular delivery efficiency, and the like.

Therefore, it is required to improve the stability of a targeting protein-drug conjugate, its half-life in a living body, and efficacy thereof.

BRIEF SUMMARY OF THE INVENTION

Provided is a chemically modified targeting protein. Also provided is a polyethyleneglycol-modified (PEGylated) targeting protein.

Further provided is a chemically modified antibody. Yet further provided is a polyethyleneglycol-modified antibody.

Still further provided is a pharmaceutical composition including a chemically modified targeting protein. Also provided is a pharmaceutical composition including a polyethyleneglycol-modified targeting protein. Also provided is a pharmaceutical composition including a chemically modified targeting antibody. Also provided is a pharmaceutical composition including a polyethyleneglycol-modified antibody.

Also provided is a conjugate including a chemically modified targeting protein and a drug.

Also provided is a conjugate including a polyethyleneglycol-modified targeting protein and a drug.

Also provided is a conjugate including a chemically modified antibody and a drug.

Also provided is a conjugate including a polyethyleneglycol-modified antibody and a drug.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a process of a process for introducing a polyethyleneglycol group to an antibody.

FIG. 2 is a photograph illustrating SDS-PAGE analysis results showing a formation of a polyethyleneglycol-introduced antibody.

FIG. 3 is a graph showing IEX-HPLC analysis results of non-reacted antibodies, polyethyleneglycol-introduced antibodies (Mono PEG Ab and Multi PEG Ab).

FIG. 4 is a graph showing a ratio between non-reacted antibodies, mono PEG Ab, and multi PEG Ab obtained from the results of FIG. 3.

FIG. 5 is a HPLC graph showing formation of antibodies where polyethyleneglycol groups with various molecular weights are introduced.

FIG. 6 is a graph showing cell growth of gastric cancer cells treated with a polyethyleneglycol-introduced antibody, wherein the “HR” of “IC_(HR)” means half-response.

FIG. 7 is a HPLC graph showing formation of polyethyleneglycol-introduced antibody-drug conjugate (PEG ADC).

FIG. 8 is a graph showing a concentration of a polyethyleneglycol-introduced antibody-drug conjugate in serum compared to that of an antibody-drug conjugate with no polyethyleneglycol, when administered in vivo.

FIG. 9 is a set of graphs showing SEC-HPLC analysis results of an unreacted antibody and polyethyleneglycol-introduced antibodies (Mono PEG Ab and Multi PEG Ab).

FIG. 10 is a set of graphs showing IEX-HPLC analysis results of an unreacted antibody and polyethyleneglycol-introduced antibodies (Mono PEG Ab and Multi PEG Ab).

DETAILED DESCRIPTION OF THE INVENTION

The disclosure relates to stabilization and multifunctionalization through a chemical modification of a targeting protein such as an antibody. When a chemically modified targeting protein provided herein is conjugated with a chemical drug, it has a considerably improved ex vivo and/or in vivo safety and stability, thereby increasing a half-life and a therapeutic efficacy of the chemical drug and solving problems in solubility which is observed when conjugating with a chemical drug, to increase the yield of a final product.

A targeting protein (compound) refers to a protein targeting a specific protein or a specific cell in a living body, and its representative example is an antibody. An intact antibody (e.g., an antibody in a complete form of an immunoglobulin such as IgG) contains an Fc group, and thus has a long life-time and excellent in vivo stability. Therefore, there has been no need to introduce a chemical functional group into an intact antibody for the purpose of increasing in vivo stability and safety. Instead, it has been tried to introduce a chemical functional group such as a PEG into an antibody fragment such as Fab fragment for increasing a half-time thereof.

Provided is a PEGylated (e.g., PEG-modified) antibody-drug conjugate (ADC), wherein a PEG molecule is introduced into a targeting protein, such as an intact antibody, and a drug is conjugated with the PEG-introduced antibody. Such PEGylated ADC can minimize its non-specific loss in a living body, to maximize an efficacy thereof, and can solve a problem of aggregation which is generally observed in ADC preparation using a hydrophobic drug.

Provided is a chemically modified targeting compound.

The targeting compound (protein) may be any compound which specifically recognizes and/or binds to a specific protein or a specific cell, and its representative example may be at least one selected from the group consisting of an antibody, an antigen-binding fragment thereof, a protein scaffold, and the like, or any combination thereof. The antibody may be an antibody (e.g., a mono-specific antibody, a bi-specific antibody, or a multi-specific antibody) or an antigen-binding fragment thereof. The antibody may be an antibody in a form including an Fc region, for example, an intact antibody (e.g., in a complete form of an immunoglobulin (IgA, IgD, IgG (IgG1, IgG2, IgG3, or IgG4), IgE, or IgM)). The antigen-binding fragment may be in a form of an antigen-binding fragment-Fc region conjugate where an antigen-binding fragment thereof (e.g., scFv, (scFv)₂, Fab, Fab′ or F(ab′)₂) is fused (linked) to an Fc region, for example a scFvFc (single stranded Fv-Fc) fragment. The intact antibody may refer to a construct comprising 1 to 5 dimers, where each dimer is in a form of a capital letter “Y”, and formed by binding two monomers, each of which is formed by linking a heavy chain and a light chain. The antibody may be at least one selected from the group consisting of IgA, IgD, IgG, IgE, and IgM, or any combination thereof, and for example, may be an antibody in an IgG form such as IgG1, IgG2, IgG3, or IgG4, or a scFvFc fragment. The scFvFc fragment refers to a single stranded fragment including a light chain variable region, a heavy chain variable region and an Fc region of an antibody, which are linked to each other.

The protein scaffold refers to a protein construct having a similar structure to an antibody (but not an antibody), and/or a protein construct specifically recognizing and/or binding to a specific protein or a specific cell. A representative example of a protein scaffold may be an antibody-derived protein scaffold or a non-antibody-derived protein scaffold. The protein scaffold may be in a protein scaffold-Fc conjugate form where a protein scaffold is fused with an Fc fragment of an antibody. The antibody-derived protein scaffold may have a similar structure (framework) to an antibody or an antigen-binding fragment thereof, and a representative example thereof may be a peptibiody, a nanobody, a domain antibody, etc. The term “peptibody”, as used herein, refers to a fusion protein (peptide+antibody) mimicking an antibody in terms of framework and function in which a peptide is fused to a partial or entire constant region, e.g., Fc, of an antibody and serves as an antigen-binging fragment (heavy chain and/or light chain CDR or variable region). The term “nanobody,” also called a single-domain antibody, as used herein, refers to an antibody fragment which possesses a monomeric single variable domain of an antibody and shows selectivity for certain antigens, like an intact antibody. Its molecular weights generally ranges from about 12 kDa to about 15 kDa, which is much smaller than that of an intact antibody (about 150 kDa to about 160 kDa) of an intact antibody (inclusive of two heavy chains and two light chains) and, in some cases, even than that of an Fab or scFv fragment.

For example, the antibody-derived protein scaffold may be at least one selected from the group consisting of blinatumomab (bispecific scFv-scFv), MT110 (bispecific scFv-scFv), Dom-0200/ART621 (domain antibody), Caplacizumab (nanobody), Ozoralizumab (nanobody), ALX-0061 (nanobody), ATN-192 (nanobody), ALX-0141 (nanobody), ALX-0171 (nanobody), and the like, or any combination thereof, but not be limited thereto. The non-antibody-derived protein scaffold may be a protein construct specifically recognizing and/or binding to a specific protein or a specific cell, besides an antibody. Examples of the non-antibody-derived protein scaffold are summarized in Table 1:

TABLE 1 Scafold Property Kunitz Domains Engineered Kunitz domains of human serine protease inhibitors that can be genetically engineered for different target protease specificities DARPins Small, engineered single domain proteins which can be selected to bind to any protein target Avimers Created from multimerized LDLR-A Anticalins Derived from lipocalins that naturally form binding sites for small ligands by means of four structurally variable loops found in the proteins Knottins Constructed from cysteine-rich knottin peptides Affibodies Based on Z-domain of staphylococcal protein A Adnectins Based on the 10th, which can adopt an Ig-like (monobodies) β- sandwich fold with two or three exposed loops without a central disulfide bridge Pronectins Based on 14th extracellular domain of human fibronectin III Fynomers 7-kDa binding proteins derived from SH3 domains of the human Fyn tyrosine kinase Nanofitins(Affitins) Structurally derived from the DNA binding protein Sac7d found in Sulfolobus acidocaldarius an archea bacterium Affilins Derived from one of two proteins; gamma- βcrystallin (a family of 20 kDa proteins found in the eye lens of vertebrates including humans) or ubiquitin (a highly conserved 76-kDa protein found in eucaryotes

The chemical modification may refer to an introduction (e.g., attachment or bonding) of a water-soluble polymer into a targeting compound. The water-soluble polymer may be introduced (attached or bound) to a targeting compound through a covalent bond. Thusly a chemically modified targeting compound has an increased stability and half-life in vivo, and can avoid aggregation when conjugated with a chemical drug such as a hydrophobic drug, thereby improving in vivo and/or ex vivo stability of the conjugated drug. The water-soluble polymer may be a polyethyleneglycol (PEG) or other water-soluble polymer. As a molecular weight of the water-soluble polymer is larger, the in vivo safety and the in vivo and/or ex vivo stability are increased, but the possibility to affect an efficacy of an antibody or a drug to be linked thereto is increase, as well. The polymer may have a weight average molecular weight of about 100 to about 1,000,000 Da, about 1000 to about 500,000 Da, or about 5000 to about 100,000 Da, but not be limited thereto. In a particular embodiment, the water-soluble polymer may be a polyethyleneglycol (PEG). The PEG may be introduced (attached or bound) to a targeting compound such as an antibody through a covalent bond, to form a conjugate with the target compound. In order to maintain an excellent in vivo safety, in vivo and/or ex vivo stability, and efficacy (biological activity), the polyethyleneglycol may have a weight average molecular weight of at least 100 Da, at least 1000 Da, at least 5,000 Da, at least 10,000 Da or at least 20,000 Da, such as about 100 to about 1,000,000 Da, 1000 to about 1,000,000 Da, about 1000 to about 500,000 Da, about 1000 to about 100,000 Da, 5000 to about 1,000,000 Da, about 5000 to about 500,000 Da, about 5000 to about 100,000 Da, 1,0000 to about 1,000,000 Da, about 10,000 to about 500,000 Da, about 10,000 to about 100,000 Da, 20,000 to about 1,000,000 Da, about 20,000 to about 500,000 Da, about 20,000 to about 100,000 Da, 3,0000 to about 1,000,000 Da, about 30,000 to about 500,000 Da, or about 30,000 to about 100,000 Da, but is not limited thereto. In some embodiments, the water-soluble polymer has an average molecular weight of at least about 1000 Da, such as at least about 5,000 Da, or at least about 10,000 Da (e.g., at least about 20,000 Da or 30,000 Da).

In the chemically modified targeting compound, a water-soluble polymer such as a polyethyleneglycol may be introduced into N-terminus of a targeting compound, or introduced into a targeting compound through a free-cysteine or a free-thiol group. In addition, in the chemically modified targeting compound, a polyethyleneglycol may be introduced into a targeting compound at the amount of 1 to 4, 1 to 3, 1 to 2, or 1 molecule of polyethyleneglycol per 1 molecule of the targeting compound.

Also provided is a chemically modified antibody. Further provided is a polyethyleneglycol-introduced (PEGylated) antibody. The antibody may be an antibody containing an Fc region, e.g., an intact antibody or an antigen-binding fragment-Fc conjugate (e.g., an scFvFc fragment). A polyethyleneglycol may be introduced into N-terminus, C-terminus, or each of N-terminus and C-terminus (when two or more polyethyleneglycol molecules are introduced) of an antibody (e.g., a heavy chain and/or a light chain of an antibody), or introduced through a free-cysteine (free Cys) or a free-thiol group which may be generated by cleavage of disulfide bond in an antibody, for example by DTT treatment. In a particular embodiment, a polyethyleneglycol may be introduced into N-terminus of an antibody, for example N-terminus of a heavy chain of an antibody. In order to make an antibody and polyethyleneglycol optimally react with each other, and to decrease aggregation and increase half-life when conjugated with a drug, a polyethyleneglycol may be introduced into an antibody at the amount of 1 to 4, 1 to 3, 1 to 2, or 1 molecule of polyethyleneglycol per 1 antibody. A position of introduction of polyethyleneglycol in an antibody may be at least one of N-termini of two heavy chains and N-termini of two light chains, for example, at least one of N-termini of two heavy chains. To generate such a modified antibody, an antibody and a polyethyleneglycol may be reacted (contacted) at a molar ratio (PEG/antibody) of about 1 to about 20, about 1 to about 15, about 1 to about 10, about 2 to about 8, or about 3 to about 7.

As described above, compared to a targeting compound and an antibody with no chemical modification or PEGylation, a chemically modified targeting compound, a chemically modified antibody, or a polyethyleneglycol-introduced antibody can achieve 1) an increased in vivo safety and an increased half-time when conjugated with a drug (e.g., a hydrophobic drug), 2) a decreased aggregation of exposed drug of the conjugate and an increased in vivo and/or ex vivo stability, and 3) a considerably decreased non-specific uptake and thus an increased efficacy and a decreased side effect of the drug. For these reasons, a chemically modified targeting compound, a chemically modified antibody, or a polyethyleneglycol-introduced antibody may be useful in a drug (e.g., a hydrophobic drug) delivery in vivo (in a living body). A drug may be used in a conjugate form which is conjugated with a chemically modified targeting compound, a chemically modified antibody, or a polyethyleneglycol.

Also provided is a pharmaceutical composition comprising a chemically modified targeting compound, a chemically modified antibody, or a polyethyleneglycol-introduced antibody. Further provided is a pharmaceutical composition for drug delivery comprising a chemically modified targeting compound, a chemically modified antibody, or a polyethyleneglycol-introduced antibody. Yet further provided is a conjugate comprising a drug and a chemically modified targeting compound, a chemically modified antibody, or a polyethyleneglycol-introduced antibody conjugated to the drug. The conjugate may be an antibody-drug conjugate (ADC) where a drug and an antibody are conjugated. Still further provided is a method for drug delivery, comprising administering a conjugate to a subject in need of administration (delivery) of a drug contained in the conjugate. The subject may be a vertebrate such as a mammal (e.g., human), a bird, and the like, who is in need of administration of a drug, or a cell or a tissue isolated therefrom or artificially prepared or a culture of the cell or tissue, for example, a diseased cell (e.g., a cancer cell) or a diseased tissue (e.g., a cancer tissue) isolated from a vertebrate, or a culture thereof, but not be limited thereto.

A drug contained in a conjugate may be at least one selected from the group consisting of a cytotoxic drug, a radioactive isotope, and a contrast substance, or any combination thereof.

In a conjugate, a chemically modified targeting compound, a chemically modified antibody, or a polyethyleneglycol-introduced antibody (hereinafter, ‘an antibody and the like’) may be linked to a drug through a chemical bond, for example, a covalent bond. For example, a drug and an antibody and the like may be linked to each other through a thiol coupling (SH coupling) or an amine coupling (NH₂ coupling). For these purpose, a drug may be derivatized so that it possesses a functional group capable of forming a thiol coupling or an amine coupling.

The functional group may be introduced (e.g., through a chemical bond such as a covalent bond, ionic bond, coordinate bond, etc.) into a drug via a linker or directly with no linker. The linker may be any compound having the following characteristics: (1) a stability in blood flow, thereby preventing a drug from being separated from an antibody in a conjugate during circulation of the conjugate with blood in a living body, maintaining the drug as a prodrug state until arriving at a target cell or tissue, to minimize a damage (toxicity) to a normal cell or tissue, and (2) a cleavage selective in a diseased cell or tissue (e.g., a cancer cell or a cancer tissue), whereby a drug is released a drug from an antibody in a conjugate, to exhibit an efficacy thereof.

The drug may be derivatized by introducing a functional group capable of forming a thiol coupling or an amine coupling via a linker or directly with no linker.

In addition, the antibody-drug conjugate can achieve a synergistic effect by exhibiting effects of the antibody and the drug together, thereby having not only a synergistic effect on a diseased cell or tissue on which the antibody alone has an effect but also an effect even on a cell or tissue having agonism or resistance to the antibody, to expand the scope of application of the antibody and/or the drug. In addition, a drug, for example, a cytotoxic drug (an anticancer drug, etc.) has a problem to induce a hepatotoxicity when applied to a living body. However, when the drug is used in an antibody-drug conjugate form by linkage with a chemically modified antibody and the like, a non-specific uptake is decreased, whereby the hepatotoxicity is considerably decreased.

Also provided is a pharmaceutical composition comprising the conjugate.

When the antibody targets a cancer-related protein as an antigen (e.g., the antibody targets an anti-c-Met antibody, etc.) and/or the drug is a cytotoxic agent (e.g., an anticancer drug), provided is a pharmaceutical composition for preventing and/or treating a cancer comprising an antibody-drug conjugate. Yet still further provided is a method of preventing and/or treating a cancer comprising administering an antibody-drug conjugate to a subject in need of preventing and/or treating a cancer. The antibody-drug conjugate may be administered in a pharmaceutically effective amount. The method may further comprise a step of identify a subject in need of preventing and/or treating a cancer, prior to a step of administering.

The subject for administration may be any animal in need of preventing and/or treating a cancer, or a cell or tissue isolated (derived) therefrom. The subject may be a mammal, for example a primate such as human, a monkey, etc., or a rodent such as a mouse, a rat, etc., a cell or tissue isolated (derived) therefrom or a culture of the cell or tissue. For example, the subject may be a cancer patient, or a cancer cell or cancer tissue isolated (derived) from the patient, or a culture of the cancer cell or cancer tissue.

Also provided is a method of preparing an antibody-drug conjugate having an increased delivery efficiency in a living body, or a method of increasing a delivery efficiency in a living body of an antibody-drug conjugate, wherein the method comprises linking a drug to a polyethyleneglycol-introduced antibody. The delivery efficiency in a living body may refer to an increase in a stability in vivo by a decrease in aggregation of an exposed drug, an increase in a half-life by an increase in a stability in vivo, a decrease in side effects (e.g., a hepatotoxicity) by a decrease in a non-specific uptake, and/or an increase in an efficacy by an increase in an amount of a drug that is delivered (transferred) to a target.

The step of linking a drug and a polyethyleneglycol-introduced antibody may comprise a steps of reacting (contacting) an antibody and a polyethyleneglycol, to produce a polyethyleneglycol-introduced antibody and reacting (contacting) a drug with the polyethyleneglycol-introduced antibody, or a step of mixing an antibody, a polyethyleneglycol, and a drug, allowing reacting between them.

In the method, the polyethyleneglycol-introduced antibody, a drug, and linkage between the antibody and the drug are described herein. That is, a polyethyleneglycol-introduced antibody may be obtained by introducing a polyethyleneglycol into N-terminus, C-terminus, or both termini of a heavy chain and/or a light chain of an antibody, or by introducing a free-cysteine (free Cys) or a free-thiol group and introducing a polyethyleneglycol through the free-cysteine (free Cys) or free-thiol group. A polyethyleneglycol molecule may be introduced into an N-terminus of an antibody, for example, N-terminus of a heavy chain of an antibody. For example, a polyethyleneglycol may be introduced into an antibody at the amount of 1 to 4, 1 to 3, 1 to 2, or 1 molecule of polyethyleneglycol per 1 molecule of an antibody. A position of introduction of polyethyleneglycol in an antibody may be at least one of N-termini of two heavy chains and N-termini of two light chains, for example, at least one of N-termini of two heavy chains. To generate such PEGylated antibody, an antibody and a polyethyleneglycol may be reacted (contacted) at a molar ratio (PEG/antibody) of about 1 to about 20, about 1 to about 15, about 1 to about 10, or about 3 to about 7. In addition, the step of linking an (PEGylated) antibody and a drug may be performed by directly linking an (PEGylated) antibody and a drug, or by further comprising a step of introducing a functional group capable of forming a thiol coupling or an amine coupling to a group (e.g., an OH group) capable of forming an ester bond in a drug through a intracellular cleavable linker or directly with no linker, prior to the step of linking an (PEGylated) antibody and a drug.

A drug to be contained in a conjugate may be any biocompatible substance having a therapeutic function or a function to maintain a bioactivity in a living body, and for example, at least one selected from the group consisting of various chemicals, peptides, proteins, nucleic acids (e.g., DNA, RNA), and the like, or any combination thereof.

The drug may be any drug having a cytotoxic activity, in particular, to a cancer cell. For example, the drug may be hydrophobic. For example, the drug may be at least one selected from the group consisting of various chemicals (e.g., an anticancer agent), peptide drugs, protein drugs, nucleic acids (e.g., antisense oligonucleotide, siRNA, shRNA, microRNA, aptamer, etc.), and the like, or any combination thereof. For example, the drug may be at least one selected from the group consisting of maytansine, auristatin-based drug, calicheamycin-based drug, pyrrolobenzodiazepine-based drug, duocarmycin, docetaxel, doxorubicin, carboplatin(paraplatin), cyclophosphamide, ifosfamide, nidran, nitrogen mustard, mechlorethamine HCL, bleomycin, mitomycin C, cytarabine, flurouracil, gemcitabine, trimetrexate, methotrexate, etoposide, vinblastine, vinorelbine, alimta, altretamine, procarbazine, paclitaxel (Taxol), taxotere, topotecan, irinotecan, and the like, or any combination thereof, but not be limited thereto.

In the drug, a functional group capable of forming a thiol coupling, an amine coupling, or a reductive amination (conjugating an amine and an aldehyde) may be introduced to a functional group capable of forming a chemical (covalent) bond (e.g., a ester bond) with an antibody, for example, an OH group, in a drug, through a intracellular cleavable linker or directly with no linker.

The functional group may be any compound capable of forming a chemical bond with an antibody (e.g., an anti-c-Met antibody) or an amino acid residue of the antibody. For example, the functional group may be at least one selected from the group consisting of maleimide-based compounds, pyridyldithio-based compounds, N-hydroxysuccinimide-based compounds and derivatives thereof, aldehydes, and the like, or any combination thereof, but not be limited thereto.

For example, the functional group capable of forming a thiol coupling may be any compound capable of reacting with (binding to) a thiol group of a cysteine residue of an antibody (e.g., an anti-c-Met antibody), and for example, at least one selected from the group consisting of maleimide-based compounds, pyridyldithio-based compounds, and the like, or any combination thereof, but not be limited thereto. The functional group capable of forming an amine coupling may be any compound capable of forming an amine bond with an amino acid residue such as lysine of an antibody (e.g., an anti-c-Met antibody), and for example, at least one selected from the group consisting of N-hydroxysuccinimide-based compounds, derivatives thereof, aldehydes, and the like, or any combination thereof, but not be limited thereto. The functional group capable of a reductive amination may be any compound capable of forming an amine bond with an amino acid residue, such as a primary amine, lysine residue, and/or N-terminal amine, of an antibody (e.g., an anti-c-Met antibody), and for example, at least one selected from the group consisting of aldehydes and the like, or any combination thereof, but not be limited thereto.

The functional group may be introduced into a drug through a linker or directly with no linker. The linker may be any compound having the following characteristics: (1) stability in the bloodstream, thereby preventing a drug from being separated from an antibody in a conjugate during circulation of the conjugate with blood in a living body, maintaining the drug as a prodrug state until arriving at a target cell or tissue, to minimize a damage (toxicity) to a normal cell or tissue, and (2) a cleavage by a peptidase or a protease selectively present in a diseased cell or tissue (e.g., a cancer cell or a cancer tissue) after being delivered into the diseased cell or tissue, whereby a drug is released a drug from an antibody in a conjugate, to exhibit a cytotoxicity. For example, the linker may be one or a compound comprising at least two, selected from the group consisting of an amino acid, an amino acid derivative, a peptide (e.g., a peptide capable of being used as a substrate of a protease or a peptidase) comprising about 1 to about 10 amino acids (e.g., about 2 to about 10 amino acids), an alkyl group having 1 to 12 carbon atoms, a hydrophilic spacer comprising about 1 to about 12 ethyleneglycol units (—CH₂CH₂—O—), and the like, or any combination thereof, but not limited thereto. For example, when an antibody is linked to a drug through a thiol coupling, the linker may be one or a compound comprising at least two, selected from the group consisting of an amino acid, a peptide (e.g., a peptide capable of being used as a substrate of a protease or a peptidase) comprising about 1 to about 10 amino acids (e.g., about 2 to about 10 amino acids), an alkyl group having 1 to 12 carbon atoms, and the like, or any combination thereof, but not limited thereto. When an antibody linked to a drug through an amine coupling, the linker may be one or a compound comprising at least two, selected from the group consisting of a hydrophilic spacer comprising about 1 to about 12 ethyleneglycol units (—CH₂CH₂—O—), and the like, or any combination thereof, but not limited thereto. When an antibody linked to a drug through a reductive amination, the linker may be one or a compound comprising at least two, selected from the group consisting of an amino acid, an amino acid derivative, a peptide (e.g., a peptide capable of being used as a substrate of a protease or a peptidase) comprising about 1 to about 10 amino acids (e.g., about 2 to about 10 amino acids), an alkyl group having 1 to 12 carbon atoms, a hydrophilic spacer comprising about 1 to about 12 ethyleneglycol units (—CH₂CH₂—O—), and the like, or any combination thereof, but not limited thereto.

The amino acid derivative may be present in various forms, such as a neurotransmitter, a hormone, a metabolic intermediate, and the like. For example, the amino acid derivative may be selected from the group consisting of a gamma-amino butyric acid (GABA), serotonin, melatonin, thyroxine, indolacetate, citrulline, ornithine, carboxyl group-substituted amino acid (e.g., carboxylglutamate etc.), hydroxyl group-substituted amino acid (e.g., hydroxyproline, hydroxylysine, allo-hydroxylysine, etc.), phosphate group-substituted amino acid (e.g., phosphoserine, etc.), C1 to C4 alkyl group-substituted amino acid (e.g., ethylglycine, ethylasparagine, methylglycine, methylisoleucine, methyllysine, methylvaline, etc.), aminoadipic acid, amino propionic acid, amino butyric acid, aminocaproic acid, aminoheptanoic acid, aminoisobutyric acid, aminopimelic acid, diaminobutyric acid, desmosine, isodesmosine, diaminopimelic acid, diaminopropionic acid, norvaline, norleucine, alloisoleucine, and the like, or any combination thereof, but not limited thereto.

For example, a derivatization of docetaxel for an amine coupling may be conducted as following Reaction Scheme 1, to produce a docetaxel derivative (III) capable of forming an amine coupling with an antibody:

For example, a derivatization of docetaxel for a thiol coupling may be conducted as following Reaction Scheme 2, to produce a docetaxel derivative (VI) capable of forming a thiol coupling with an antibody:

As used herein, an antibody may be an antibody containing an Fc region, for example, an intact antibody or an scFvFc (single stranded Fv-Fc) fragment. An intact antibody may refer to a construct comprising 1 to 5 dimers, where each dimer has a structure of a capital letter “Y”, and is formed by binding two monomers, each of which is formed by linking a heavy chain and a light chain. An antibody may be at least one selected from the group consisting of IgA, IgD, IgG, IgE, and IgM, or any combination thereof, and for example, may be an intact antibody in an IgG form such as IgG1, IgG2, IgG3, or IgG4, or a scFvFc fragment thereof. The scFvFc fragment refers to a single stranded fragment including a light chain variable region, a heavy chain variable region and an Fc region of an antibody, which are linked to each other.

An antibody may specifically recognize and/or bind to an antigen which is expressed or displayed on a surface or periphery of a target cell, allowing an antibody-drug conjugate to easily target a target cell or tissue. An antibody may not only specifically recognize and/or bind to a cancer (tumor) related protein, allowing an antibody-drug conjugate to easily target a cancer (tumor) cell or tissue, but also exhibit its innate anticancer effect, leading to a synergistic effect together with the effect of a drug in the conjugate. The cancer (tumor) related protein may be at least one selected from the group consisting of cell signal transduction proteins (e.g., various growth factors, etc.), proteins on cell membrane such as receptors (e.g., receptor tyrosine kinase proteins, etc.), and the like, or any combination thereof. Examples of the growth factor may be at least one selected from the group consisting of epidermal growth factor (EGF), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), and the like, or any combination thereof. Examples of the receptor tyrosine kinase protein may be at least one selected from receptors of various growth factors, and for example, be at least one selected from the group consisting of an ErbB family such as epidermal growth factor receptor (EGFR), HER2, HERS, etc., insulin receptor, platelet-derived growth factor receptor (PDGFR), fibroblast growth factor receptor (FGFR), vascular endothelial growth factor receptor (VEGFR), hepatocyte growth factor receptor (HGFR) such as c-Met, tropomyosin-receptor-kinase (Trk) receptor, Ephrin (Eph) receptor, AXL receptor, leukocyte receptor tyrosine kinase (LTK) receptor, TIE receptor, receptor tyrosine kinase-like orphan (ROR) receptor, discoidin domain receptor (DDR), RET receptor, KLG receptor, related to receptor tyrosine kinase (RYK) receptor, Muscle-Specific Kinase (MuSK) receptor, and the like, or any combination thereof.

The antibody may be an anti-c-Met antibody recognizing c-Met as an antigen. For example, the anti-c-Met antibody may be any antibody or antigen-binding fragment thereof that acts on c-Met to induce intracellular internalization and degradation of c-Met. The anti-c-Met antibody may be any one recognizing a specific region of c-Met, e.g., a specific region in the SEMA domain, as an epitope. As described the above, the anti-c-Met antibody is characterized by specifically recognizing and binding to c-Met, and then, moving into a cell (cell-internalization). Due to such characteristics of the anti-c-Met antibody, the efficiency of the internalization of a drug conjugated to the antibody is increased, thereby increasing the efficacy of the drug.

The “c-Met protein” refers to a receptor tyrosine kinase binding to hepatocyte growth factor. The c-Met proteins may be derived from any species, for example, those derived from primates such as human c-Met (e.g., NP_(—)000236) and monkey c-Met (e.g., Macaca mulatta, NP_(—)001162100), or those derived from rodents such as mouse c-Met (e.g., NP_(—)032617.2) and rat c-Met (e.g., NP_(—)113705.1). The proteins include, for example, a polypeptide encoded by the nucleotide sequence deposited under GenBank Accession Number NM_(—)000245, or a protein encoded by the polypeptide sequence deposited under GenBank Accession Number NM_(—)000236, or extracellular domains thereof. The receptor tyrosine kinase c-Met is involved in several mechanisms including cancer incidence, cancer metastasis, cancer cell migration, cancer cell penetration, angiogenesis, etc.

c-Met, a receptor for hepatocyte growth factor (HGF), may be divided into three portions: extracellular, transmembrane, and intracellular. The extracellular portion is composed of an α-subunit and a β-subunit which are linked to each other through a disulfide bond, and contains a SEMA domain responsible for binding HGF, a PSI domain (plexin-semaphorins-integrin homology domain) and an IPT domain (immunoglobulin-like fold shared by plexins and transcriptional factors domain). The SEMA domain of c-Met protein may have the amino acid sequence of SEQ ID NO: 79, and is an extracellular domain that functions to bind HGF. A specific region of the SEMA domain, that is, a region having the amino acid sequence of SEQ ID NO: 71, which corresponds to a range from amino acid residues 106 to 124 of the amino acid sequence of the SEMA domain (SEQ ID NO: 79) of c-Met protein, is a loop region between the second and the third propellers within the epitopes of the SEMA domain. The region acts as an epitope for the specific anti-c-Met antibody of the present disclosure.

The term “epitope” as used herein, refers to an antigenic determinant, a part of an antigen recognized by an antibody. The epitope may be a region including 5 or more contiguous (consecutive or non-consecutive) amino acid residues within the SEMA domain (SEQ ID NO: 79) of c-Met protein, for instance, 5 to 19 contiguous amino acid residues within the amino acid sequence of SEQ ID NO: 71. The epitope may be a polypeptide having 5 to 19 contiguous amino acids selected from among partial combinations of the amino acid sequence of SEQ ID NO: 71, wherein the polypeptide essentially includes the amino sequence of SEQ ID NO: 73 (EEPSQ) serving as an essential element for the epitope. For example, the epitope may be a polypeptide comprising, consisting essentially of, or consisting of the amino acid sequence of SEQ ID NO: 71, SEQ ID NO: 72, or SEQ ID NO: 73. Contiguous amino acids may be consecutive amino acids in the linear sequence, or contiguous in a three-dimensional configuration of the epitope without necessarily being consecutive in the linear sequence.

The epitope having the amino acid sequence of SEQ ID NO: 72 corresponds to the outermost part of the loop between the second and third propellers within the SEMA domain of a c-Met protein. The epitope having the amino acid sequence of SEQ ID NO: 73 is a site to which the antibody or antigen-binding fragment according to one embodiment most specifically binds.

Thus, the anti-c-Met antibody may specifically bind to an epitope which has 5 to 19 contiguous amino acids selected from among partial combinations of the amino acid sequence of SEQ ID NO: 71, including SEQ ID NO: 73 as an essential element. For example, the anti-c-Met antibody may specifically bind to an epitope including the amino acid sequence of SEQ ID NO: 71, SEQ ID NO: 72, or SEQ ID NO: 73.

The anti-c-Met antibody or an antigen-binding fragment thereof may comprise or consist essentially of:

at least one heavy chain complementarity determining region (CDR) selected from the group consisting of (a) a CDR-H1 having the amino acid sequence of SEQ ID NO: 4; (b) a CDR-H2 having the amino acid sequence of SEQ ID NO: 5, SEQ ID NO: 2, or an amino acid sequence having 8-19 consecutive amino acids within SEQ ID NO: 2, wherein the 8-19 consecutive amino acids includes amino acid residues from the 3^(rd) to 10^(th) positions of SEQ ID NO: 2; and (c) a CDR-H3 having the amino acid sequence of SEQ ID NO: 6, SEQ ID NO: 85, or an amino acid sequence having 6-13 consecutive amino acids within SEQ ID NO: 85 wherein the 6-13 consecutive amino acids includes amino acid residues from the 1^(st) to 6^(th) positions of SEQ ID NO: 85, or a heavy chain variable region including the at least one heavy chain complementarity determining region;

at least one light chain complementarity determining region (CDR) selected from the group consisting of (a) a CDR-L1 having the amino acid sequence of SEQ ID NO: 7, (b) a CDR-L2 having the amino acid sequence of SEQ ID NO: 8, and (c) a CDR-L3 having the amino acid sequence of SEQ ID NO: 9, SEQ ID NO: 15, SEQ ID NO: 86, or an amino acid sequence having 9-17 consecutive amino acids within SEQ ID NO: 89 wherein the 9-17 consecutive amino acids includes amino acid residues from the 1^(st) to 9^(th) positions of SEQ ID NO: 89, or a light chain variable region including the at least one light chain complementarity determining region;

a combination of the at least one heavy chain complementarity determining region and at least one light chain complementarity determining region; or

a combination of the heavy chain variable region and the light chain variable region.

Herein, the amino acid sequences of SEQ ID NOS: 4 to 9 are respectively represented by following Formulas I to VI, below:

Xaa₁-Xaa₂-Tyr-Tyr-Met-Ser (SEQ ID NO: 4),  Formula I

wherein Xaa₁ is absent or Pro or Ser, and Xaa₂ is Glu or Asp,

Arg-Asn-Xaa₃-Xaa₄-Asn-Gly-Xaa₅-Thr (SEQ ID NO: 5),  Formula II

wherein Xaa₃ is Asn or Lys, Xaa₄ is Ala or Val, and Xaa₅ is Asn or Thr,

Asp-Asn-Trp-Leu-Xaa₆-Tyr (SEQ ID NO: 6),  Formula III

wherein Xaa₆ is Ser or Thr,

Lys-Ser-Ser-Xaa₇-Ser-Leu-Leu-Ala-Xaa₈-Gly-Asn-Xaa₉-Xaa₁₀-Asn-Tyr-Leu-Ala (SEQ ID NO: 7)  Formula IV

wherein Xaa₇ is His, Arg, Gln, or Lys, Xaa₈ is Ser or Tip, Xaa₉ is His or Gln, and Xaa₁₀ is Lys or Asn,

Trp-Xaa₁₁-Ser-Xaa₁₂-Arg-Val-Xaa₁₃(SEQ ID NO: 8)  Formula V

wherein Xaa₁₁ is Ala or Gly, Xaa₁₂ is Thr or Lys, and Xaa₁₃ is Ser or Pro, and

Xaa₁₄-Gln-Ser-Tyr-Ser-Xaa₁₅-Pro-Xaa₁₆-Thr (SEQ ID NO: 9)  Formula VI

wherein Xaa₁₄ is Gly, Ala, or Gln, Xaa₁₅ is Arg, His, Ser, Ala, Gly, or Lys, and Xaa₁₆ is Leu, Tyr, Phe, or Met.

The CDR-H1 may comprise or consist essentially of an amino acid sequence selected from the group consisting of SEQ ID NOS: 1, 22, 23, and 24. The CDR-H2 may comprise or consist essentially of an amino acid sequence selected from the group consisting of SEQ ID NOS: 2, 25, and 26. The CDR-H3 may comprise or consist essentially of an amino acid sequence selected from the group consisting of SEQ ID NOS: 3, 27, 28, and 85.

The CDR-L1 may comprise or consist essentially of an amino acid sequence selected from the group consisting of SEQ ID NOS: 10, 29, 30, 31, 32, 33, and 106. The CDR-L2 may comprise or consist essentially of an amino acid sequence selected from the group consisting of SEQ ID NOS: 11, 34, 35, and 36. The CDR-L3 may comprise or consist essentially of an amino acid sequence selected from the group consisting of SEQ ID NOS: 12, 13, 14, 15, 16, 37, 86, and 89.

The antibody or antigen-binding fragment may comprise or consist essentially of:

a heavy chain complementarity determining region (CDR) comprising a polypeptide (CDR-H1) comprising or consisting essentially of an amino acid sequence selected from the group consisting of SEQ ID NOS: 1, 22, 23, and 24, a polypeptide (CDR-H2) comprising or consisting essentially of an amino acid sequence selected from the group consisting of SEQ ID NOS: 2, 25, and 26, and a polypeptide (CDR-H3) comprising or consisting essentially of an amino acid sequence selected from the group consisting of SEQ ID NOS: 3, 27, 28, and 85 or a heavy chain variable region comprising the heavy chain complementarity determining region;

a light chain complementarity determining region comprising a polypeptide (CDR-L1) comprising or consisting essentially of an amino acid sequence selected from the group consisting of SEQ ID NOS: 10, 29, 30, 31, 32, 33 and 106, a polypeptide (CDR-L2) comprising or consisting essentially of an amino acid sequence selected from the group consisting of SEQ ID NOS: 11, 34, 35, and 36, and a polypeptide (CDR-L3) comprising or consisting essentially of an amino acid sequence selected from the group consisting of SEQ ID NOS: 12, 13, 14, 15, 16, 37, 86, and 89, or a light chain variable region comprising the light chain complementarity determining region;

a combination of the heavy chain complementarity determining region and the light chain complementarity determining region; or

a combination of the heavy chain variable region and the light chain variable region.

The variable region of the heavy chain of the anti-c-Met antibody or antigen-binding fragment may comprise or consist essentially of the amino acid sequence of SEQ ID NO: 17, 74, 87, 90, 91, 92, 93, or 94 and the variable region of the light chain may comprise or consist essentially of the amino acid sequence of SEQ ID NO: 109, 18, 19, 20, 21, 75, 88, 95, 96, 97, 98, 99, or 107.

Animal-derived antibodies produced by immunizing non-immune animals with a desired antigen generally invoke immunogenicity when injected to humans for the purpose of medical treatment, and thus chimeric antibodies have been developed to inhibit such immunogenicity. Chimeric antibodies are prepared by replacing constant regions of animal-derived antibodies that cause an anti-isotype response with constant regions of human antibodies by genetic engineering. Chimeric antibodies are considerably improved in an anti-isotype response compared to animal-derived antibodies, but variable regions of such antibodies still have animal-derived amino acid sequences, so that chimeric antibodies have side effects with respect to a potential anti-idiotype response. Humanized antibodies have been developed to reduce such side effects. Humanized antibodies are produced by grafting complementarity determining regions (CDR) which serve an important role in antigen binding in variable regions of chimeric antibodies into a human antibody framework.

An important consideration in CDR grafting to produce humanized antibodies is choosing the optimized human antibodies for accepting CDRs of animal-derived antibodies. Antibody databases, analysis of a crystal structure, and technology for molecule modeling are used. However, even when the CDRs of animal-derived antibodies are grafted to the most optimized human antibody framework, amino acids positioned in a framework of the animal-derived CDRs affecting antigen binding are present. Therefore, in many cases, antigen binding affinity is not maintained, and thus application of additional antibody engineering technology for recovering the antigen binding affinity is necessary.

The anti c-Met antibodies may be mouse-derived antibodies, mouse-human chimeric antibodies, humanized antibodies, or human antibodies. The antibodies or antigen-binding fragments thereof may be isolated from a living body or non-naturally occurring. The antibodies or antigen-binding fragments thereof may be recombinant or synthetic.

An intact antibody includes two full-length light chains and two full-length heavy chains, in which each light chain is linked to a heavy chain by disulfide bonds. The antibody has a heavy chain constant region and a light chain constant region. The heavy chain constant region is of a gamma (γ), mu (μ), alpha (α), delta (δ), or epsilon (ε) type, which may be further categorized as gamma 1 (γ1), gamma 2 (γ2), gamma 3 (γ3), gamma 4 (γ4), alpha 1 (α1), or alpha 2 (α2). The light chain constant region is of either a kappa (κ) or lambda (λ) type.

As used herein, the term “heavy chain” refers to full-length heavy chain, and fragments thereof, including a variable region V_(H) that includes amino acid sequences sufficient to provide specificity to antigens, and three constant regions, C_(H1), C_(H2), and C_(H3), and a hinge. The term “light chain” refers to a full-length light chain and fragments thereof, including a variable region V_(L) that includes amino acid sequences sufficient to provide specificity to antigens, and a constant region C_(L).

The term “complementarity determining region (CDR)” refers to an amino acid sequence found in a hyper variable region of a heavy chain or a light chain of immunoglobulin. The heavy and light chains may respectively include three CDRs (CDRH1, CDRH2, and CDRH3; and CDRL1, CDRL2, and CDRL3). The CDR may provide contact residues that play an important role in the binding of antibodies to antigens or epitopes. The terms “specifically binding” and “specifically recognized” are well known to one of ordinary skill in the art, and indicate that an antibody and an antigen specifically interact with each other to lead to an immunological activity.

The term “antigen-binding fragment” used herein refers to fragments of an intact immunoglobulin including portions of a polypeptide including antigen-binding regions having the ability to specifically bind to the antigen. The antigen-binding fragment may be scFv, (scFv)₂, scFvFc, Fab, Fab′, or F(ab′)₂, but is not limited thereto.

Among the antigen-binding fragments, Fab that includes light chain and heavy chain variable regions, a light chain constant region, and a first heavy chain constant region C_(H1), has one antigen-binding site.

The Fab′ fragment is different from the Fab fragment, in that Fab′ includes a hinge region with at least one cysteine residue at the C-terminal of C_(H1).

The F(ab′)₂ antibody is formed through disulfide bridging of the cysteine residues in the hinge region of the Fab′ fragment.

Fv is the smallest antibody fragment with only a heavy chain variable region and a light chain variable region. Recombination techniques of generating the Fv fragment are widely known in the art.

Two-chain Fv includes a heavy chain variable region and a light chain region which are linked by a non-covalent bond. Single-chain Fv generally includes a heavy chain variable region and a light chain variable region which are linked by a covalent bond via a peptide linker or linked at the C-terminals to have a dimer structure like the two-chain Fv. The peptide linker may be the same as described in the above, for example, those including the amino acid length of about 1 to about 100, about 2 to about 50, particularly about 5 to about 25, and any kinds of amino acids may be included without any restrictions.

The antigen-binding fragments may be attainable using protease (for example, the Fab fragment may be obtained by restricted cleavage of a whole antibody with papain, and the F(ab′)₂ fragment may be obtained by cleavage with pepsin), or may be prepared by using a genetic recombination technique.

The term “hinge region,” as used herein, refers to a region between CH1 and CH2 domains within the heavy chain of an antibody which functions to provide flexibility for the antigen-binding site.

When an animal antibody undergoes a chimerization process, the IgG1 hinge of animal origin is replaced with a human IgG1 hinge or IgG2 hinge while the disulfide bridges between two heavy chains are reduced from three to two in number. In addition, an animal-derived IgG1 hinge is shorter than a human IgG1 hinge. Accordingly, the rigidity of the hinge is changed. Thus, a modification of the hinge region may bring about an improvement in the antigen binding efficiency of the humanized antibody. The modification of the hinge region through amino acid deletion, addition, or substitution is well-known to those skilled in the art.

The anti-c-Met antibody or an antigen-binding fragment thereof may be modified by the deletion, insertion, addition, or substitution of at least one amino acid residue on the amino acid sequence of the hinge region so that it exhibit enhanced antigen-binding efficiency. For example, the antibody may include a hinge region including the amino acid sequence of SEQ ID NO: 100(U7-HC6), 101(U6-HC7), 102(U3-HC9), 103(U6-HC8), or 104(U8-HC5), or a hinge region including the amino acid sequence of SEQ ID NO: 105 (non-modified human hinge). In particular, the hinge region has the amino acid sequence of SEQ ID NO: 100 or 101.

The anti-c-Met antibody may be a monoclonal antibody. The monoclonal antibody may be produced by the hybridoma cell line deposited with Accession No. KCLRF-BP-00220, which binds specifically to the extracellular region of c-Met protein (refer to Korean Patent Publication No. 2011-0047698, the disclosure of which is incorporated in its entirety herein by reference). The anti-c-Met antibody may include any of the antibodies defined in Korean Patent Publication No. 2011-0047698, the disclosure of which is hereby incorporated by reference.

In the anti-c-Met antibody, the rest portion of the light chain and the heavy chain portion excluding the CDRs, the light chain variable region, and the heavy chain variable region as defined above, that is the light chain constant region and the heavy chain constant region, may be those from any subtype of immunoglobulin (e.g., IgA, IgD, IgE, IgG (IgG1, IgG2, IgG3, IgG4), IgM, and the like).

By way of further example, the anti-c-Met antibody or the antibody fragment may comprise or consist essentially of:

a heavy chain including the amino acid sequence selected from the group consisting of the amino acid sequence of SEQ ID NO: 62 (wherein the amino acid sequence from amino acid residues from the 1^(st) to 17^(th) positions is a signal peptide), or the amino acid sequence from the 18^(th) to 462^(nd) positions of SEQ ID NO: 62, the amino acid sequence of SEQ ID NO: 64 (wherein the amino acid sequence from the 1^(st) to 17^(th) positions is a signal peptide), the amino acid sequence from the 18^(th) to 461^(st) positions of SEQ ID NO: 64, the amino acid sequence of SEQ ID NO:66 (wherein the amino acid sequence from the 1^(st) to 17^(th) positions is a signal peptide), and the amino acid sequence from the 18^(th) to 460^(th) positions of SEQ ID NO: 66; and

a light chain including the amino acid sequence selected from the group consisting of the amino acid sequence of SEQ ID NO: 68 (wherein the amino acid sequence from the 1^(st) to 20^(th) positions is a signal peptide), the amino acid sequence from the 21^(st) to 240^(th) positions of SEQ ID NO: 68, the amino acid sequence of SEQ ID NO: 70 (wherein the amino acid sequence from the 1^(st) to 20^(th) positions is a signal peptide), the amino acid sequence from the 21^(st) to 240^(th) positions of SEQ ID NO: 70, and the amino acid sequence of SEQ ID NO: 108.

For example, the anti-c-Met antibody may be selected from the group consisting of:

an antibody including a heavy chain including the amino acid sequence of SEQ ID NO: 62 or the amino acid sequence from the 18^(th) to 462^(nd) positions of SEQ ID NO: 62 and a light chain including the amino acid sequence of SEQ ID NO: 68 or the amino acid sequence from the 21^(st) to 240^(th) positions of SEQ ID NO: 68;

an antibody including a heavy chain including the amino acid sequence of SEQ ID NO: 64 or the amino acid sequence from the 18^(th) to 461^(st) positions of SEQ ID NO: 64 and a light chain including the amino acid sequence of SEQ ID NO: 68 or the amino acid sequence from the 21^(st) to 240^(th) positions of SEQ ID NO: 68;

an antibody including a heavy chain including the amino acid sequence of SEQ ID NO: 66 or the amino acid sequence from the 18^(th) to 460^(th) positions of SEQ ID NO: 66 and a light chain including the amino acid sequence of SEQ ID NO: 68 or the amino acid sequence from the 21^(st) to 240^(th) positions of SEQ ID NO: 68;

an antibody including a heavy chain including the amino acid sequence of SEQ ID NO: 62 or the amino acid sequence from the 18^(th) to 462^(nd) positions of SEQ ID NO: 62 and a light chain including the amino acid sequence of SEQ ID NO: 70 or the amino acid sequence from the 21^(st) to 240^(th) positions of SEQ ID NO: 70;

an antibody including a heavy chain including the amino acid sequence of SEQ ID NO: 64 or the amino acid sequence from the 18^(th) to 461^(st) positions of SEQ ID NO: 64 and a light chain including the amino acid sequence of SEQ ID NO: 70 or the amino acid sequence from the 21^(st) to 240^(th) positions of SEQ ID NO: 70;

an antibody including a heavy chain including the amino acid sequence of SEQ ID NO: 66 or the amino acid sequence from the 18^(th) to 460^(th) positions of SEQ ID NO: 66 and a light chain including the amino acid sequence of SEQ ID NO: 70 or the amino acid sequence from the 21^(st) to 240^(th) positions of SEQ ID NO: 70;

an antibody including a heavy chain including the amino acid sequence of SEQ ID NO: 62 or the amino acid sequence from the 18^(th) to 462^(nd) positions of SEQ ID NO: 62 and a light chain including the amino acid sequence of SEQ ID NO: 108;

an antibody including a heavy chain including the amino acid sequence of SEQ ID NO: 64 or the amino acid sequence from the 18^(th) to 461^(st) positions of SEQ ID NO: 64 and a light chain including the amino acid sequence of SEQ ID NO: 108; and

an antibody including a heavy chain including the amino acid sequence of SEQ ID NO: 66 or the amino acid sequence from the 18^(th) to 460^(th) positions of SEQ ID NO: 66 and a light chain including the amino acid sequence of SEQ ID NO: 108.

The anti-c-Met antibody may include a heavy chain including the amino acid sequence from the 18^(th) to 460^(th) positions of SEQ ID NO: 66 and a light chain including the sequence from the 21^(st) to 240^(th) positions of SEQ ID NO: 68, or a heavy chain including the amino acid sequence from the 18^(th) to 460^(th) positions of SEQ ID NO: 66 and a light chain including the sequence of SEQ ID NO: 108.

The polypeptide of SEQ ID NO: 70 is a light chain including human kappa (κ) constant region, and the polypeptide with the amino acid sequence of SEQ ID NO: 68 is a polypeptide obtained by replacing histidine at position 62 (corresponding to position 36 of SEQ ID NO: 68 according to kabat numbering) of the polypeptide with the amino acid sequence of SEQ ID NO: 70 with tyrosine. The production yield of the antibodies may be increased by the replacement. The polypeptide with the amino acid sequence of SEQ ID NO: 108 is a polypeptide obtained by replacing serine at position 32 of the polypeptide with the amino acid sequence of SEQ ID NO: 108 (corresponding to position 52 of SEQ ID NO: 68, which corresponds to position 27e according to kabat numbering in the amino acid sequence from amino acid residues 21 to 240 of SEQ ID NO: 68; positioned within CDR-L1) with tryptophan. By such replacement, antibodies and antibody fragments including such sequences exhibits increased activities, such as c-Met biding affinity, c-Met degradation activity, Akt phosphorylation inhibition, and the like.

The antibody may be at least one selected from the group consisting of trastuzumab, pertuzumab, Trastuzumab emtansine (T-DM1), bevacizumab, cetuximab, ramucirumab, and the like, or any combination thereof, but not be limited thereto.

In the antibody-drug conjugate, the number of drugs (or drug derivatives wherein a functional group is introduced through a linker or directly with no linker in order to bind to an antibody) which bind to one antibody may be an integer from about 1 to about 10 (see FIGS. 5 and 7). When two or more drugs are conjugated with one antibody, each drug may be the same with or different from one another.

In addition, in order to increase a yield of a conjugate by minimizing aggregation, oligomerization, dimerization, and the like, the molar ratio (DAR; drug-to-antibody ratio; mole of drug/mole of antibody) between an antibody and a drug in a conjugate may be about 1 to about 20, about 1 to about 15, about 1 to about 10, about 2 to about 8, about 3 to about 7, about 3 to about 6, or about 3.3 to about 5.5.

The conjugate or the pharmaceutical composition may be administered or formulated along with a pharmaceutically acceptable carrier, diluent, and/or excipient.

The pharmaceutically acceptable carrier to be included in the conjugate or the composition may be those commonly used for the formulation of drugs, which may be one or more selected from the group consisting of lactose, dextrose, sucrose, sorbitol, mannitol, starch, gum acacia, calcium phosphate, alginates, gelatin, calcium silicate, micro-crystalline cellulose, polyvinylpyrrolidone, cellulose, water, syrup, methyl cellulose, methylhydroxy benzoate, propylhydroxy benzoate, talc, magnesium stearate, and mineral oil, but are not limited thereto. The pharmaceutical composition may further include one or more selected from the group consisting of a lubricant, a wetting agent, a sweetener, a flavor enhancer, an emulsifying agent, a suspension agent, and preservative.

The conjugate or the pharmaceutical composition may be administered orally or parenterally. The parenteral administration may include intravenous injection, subcutaneous injection, muscular injection, intraperitoneal injection, endothelial administration, local administration, intranasal administration, intrapulmonary administration, and rectal administration. Since oral administration leads to digestion of proteins or peptides, an active ingredient in the compositions for oral administration must be coated or formulated to prevent digestion in stomach. In addition, the compositions may be administered using an optional device that enables an active substance to be delivered to target cells.

The term “the pharmaceutically effective amount” as used in this specification refers to an amount of an active ingredient (e.g., a conjugate) can exert pharmaceutically significant effects. The pharmaceutically effective amount of the conjugate or the pharmaceutical composition for a single dose may be prescribed in a variety of ways, depending on factors such as formulation methods, administration manners, age of patients, body weight, gender, pathologic conditions, diets, administration time, administration interval, administration route, excretion speed, and reaction sensitivity. For example, the pharmaceutically effective amount of the conjugate or the active ingredient (i.e., the conjugate) in the pharmaceutical composition for a single dose may be in ranges of 0.001 to 100 mg/kg, or 0.02 to 50 mg/kg, but not limited thereto.

The pharmaceutically effective amount for the single dose may be formulated into a single formulation in a unit dosage form or formulated in suitably divided dosage forms, or it may be manufactured to be contained in a multiple dosage container.

The conjugate or the pharmaceutical composition may be formulated with a pharmaceutically acceptable carrier and/or excipient into a unit or a multiple dosage form by a method easily carried out by a skilled person in the pertinent art. The dosage form may be a solution in oil or an aqueous medium, a suspension, syrup, an emulsifying solution, an extract, powder, granules, a tablet, or a capsule, and may further include a dispersing or a stabilizing agent.

The cancer to be applied the pharmaceutical composition may be a solid cancer or hematological cancer and for instance, may be, but not limited to, one or more selected from the group consisting of squamous cell carcinoma, small-cell lung cancer, non-small-cell lung cancer, adenocarcinoma of the lung, squamous cell carcinoma of the lung, peritoneal carcinoma, skin cancer, melanoma in the skin or eyeball, rectal cancer, cancer near the anus, esophagus cancer, small intestinal tumor, endocrine gland cancer, parathyroid cancer, adrenal cancer, soft-tissue sarcoma, urethral cancer, chronic or acute leukemia, lymphocytic lymphoma, hepatoma, gastric cancer, gastric cancer, gastrointestinal cancer, pancreatic cancer, glioblastoma, cervical cancer, ovarian cancer, liver cancer, bladder cancer, hepatocellular adenoma, breast cancer, colon cancer, large intestine cancer, endometrial carcinoma or uterine carcinoma, salivary gland tumor, kidney cancer, prostate cancer, vulvar cancer, thyroid cancer, head or neck cancer, brain cancer, osteosarcoma, and the like. The scope of the cancer can be expanded to a cancer having a resistance to a drug and/or an antibody used in the conjugate. The cancer may be a primary cancer or a metastatic cancer.

A chemically modified targeting protein, for example, a polyethyleneglycol-introduced antibody, provided herein, has considerably improved pharmacokinetic properties, to reduce aggregation when conjugated with a drug such as a hydrophobic drug, thereby increasing in vivo or ex vivo stability and decreasing a half-life, and it reduces a non-specific uptake, to minimize the loss of an antibody and/or a drug, thereby maximizing efficacies and minimizing side effects.

EXAMPLES

The following examples are intended merely to illustrate the invention and are not to be construed to restrict the invention.

Reference Example 1 Construction of Anti-c-Met Antibody

1.1. Production of “AbF46”, a Mouse Antibody to c-Met

1.1.1. Immunization of Mouse

To obtain immunized mice necessary for the development of a hybridoma cell line, each of five BALB/c mice (Japan SLC, Inc.), 4 to 6 weeks old, was intraperitoneally injected with a mixture of 100 μg of human c-Met/Fc fusion protein (R&D Systems) and one volume of complete Freund's adjuvant. Two weeks after the injection, a second intraperitoneal injection was conducted on the same mice with a mixture of 50 μg of human c-Met/Fc protein and one volume of incomplete Freund's adjuvant. One week after the second immunization, the immune response was finally boosted. Three days later, blood was taken from the tails of the mice and the sera were 1/1000 diluted in PBS and used to examine a titer of antibody to c-Met by ELISA. Mice found to have a sufficient antibody titer were selected for use in the cell fusion process.

1.1.2. Cell Fusion and Production of Hybridoma

Three days before cell fusion, BALB/c mice (Japan SLC, Inc.) were immunized with an intraperitoneal injection of a mixture of 50 μg of human c-Met/Fc fusion protein and one volume of PBS. The immunized mice were anesthetized before excising the spleen from the left half of the body. The spleen was meshed to separate splenocytes which were then suspended in a culture medium (DMEM, GIBCO, Invitrogen). The cell suspension was centrifuged to recover the cell layer. The splenocytes thus obtained (1×10⁸ cells) were mixed with myeloma cells (Sp2/0) (1×10⁸ cells), followed by spinning to give a cell pellet. The cell pellet was slowly suspended, treated with 45% polyethylene glycol (PEG) (1 mL) in DMEM for 1 min at 37° C., and supplemented with 1 mL of DMEM. To the cells was added 10 mL of DMEM over 10 min, after which incubation was conducted in a water bath at 37° C. for 5 min. Then the cell volume was adjusted to 50 mL before centrifugation. The cell pellet thus formed was resuspended at a density of 1˜2×10⁵ cells/mL in a selection medium (HAT medium) and 0.1 mL of the cell suspension was allocated to each well of 96-well plates which were then incubated at 37° C. in a CO₂ incubator to establish a hybridoma cell population.

1.1.3. Selection of Hybridoma Cells Producing Monoclonal Antibodies to c-Met Protein

From the hybridoma cell population established in Reference Example 1.1.2, hybridoma cells which showed a specific response to c-Met protein were screened by ELISA using human c-Met/Fc fusion protein and human Fc protein as antigens.

Human c-Met/Fc fusion protein was seeded in an amount of 50 μL (2 μg/mL)/well to microtiter plates and allowed to adhere to the surface of each well. The antibody that remained unbound was removed by washing. For use in selecting the antibodies that do not bind c-Met but recognize Fc, human Fc protein was attached to the plate surface in the same manner.

The hybridoma cell culture obtained in Reference Example 1.1.2 was added in an amount of 50 μL to each well of the plates and incubated for 1 hour. The cells remaining unreacted were washed out with a sufficient amount of Tris-buffered saline and Tween 20 (TBST). Goat anti-mouse IgG-horseradish peroxidase (HRP) was added to the plates and incubated for 1 hour at room temperature. The plates were washed with a sufficient amount of TBST, followed by reacting the peroxidase with a substrate (OPD). Absorbance at 450 nm was measured on an ELISA reader.

Hybridoma cell lines which secrete antibodies that specifically and strongly bind to human c-Met but not human Fc were selected repeatedly. From the hybridoma cell lines obtained by repeated selection, a single clone producing a monoclonal antibody was finally separated by limiting dilution. The single clone of the hybridoma cell line producing the monoclonal antibody was deposited with the Korean Cell Line Research Foundation, an international depository authority located at Yungun-Dong, Jongno-Gu, Seoul, Korea, on Oct. 6, 2009, with Accession No. KCLRF-BP-00220 according to the Budapest Treaty (refer to Korean Patent Laid-Open Publication No. 2011-0047698).

1.1.4. Production and Purification of Monoclonal Antibody

The hybridoma cell line obtained in Reference Example 1.1.3 was cultured in a serum-free medium, and the monoclonal antibody (AbF46) was produced and purified from the cell culture.

First, the hybridoma cells cultured in 50 mL of a medium (DMEM) supplemented with 10% (v/v) FBS were centrifuged and the cell pellet was washed twice or more with 20 mL of PBS to remove the FBS therefrom. Then, the cells were resuspended in 50 mL of DMEM and incubated for 3 days at 37° C. in a CO₂ incubator.

After the cells were removed by centrifugation, the supernatant was stored at 4° C. before use or immediately used for the separation and purification of the antibody. An AKTA system (GE Healthcare) equipped with an affinity column (Protein G agarose column; Pharmacia, USA) was used to purify the antibody from 50 to 300 mL of the supernatant, followed by concentration with a filter (Amicon). The antibody in PBS was stored before use in the following examples.

1.2. Construction of chAbF46, a Chimeric Antibody to c-Met

A mouse antibody is apt to elicit immunogenicity in humans. To solve this problem, chAbF46, a chimeric antibody, was constructed from the mouse antibody AbF46 produced in Experimental Example 1.1.4 by replacing the constant region, but not the variable region responsible for antibody specificity, with an amino sequence of the human IgG1 antibody.

In this regard, a gene was designed to include the nucleotide sequence of “EcoRI-signal sequence-VH-NheI-CH-TGA-XhoI” (SEQ ID NO: 38) for a heavy chain and the nucleotide sequence of “EcoRI-signal sequence-VL-BsiWI-CL-TGA-XhoI” (SEQ ID NO: 39) for a light chain and synthesized. Then, a DNA fragment having the heavy chain nucleotide sequence (SEQ ID NO: 38) and a DNA fragment having the light chain nucleotide sequence (SEQ ID NO: 39) were digested with EcoRI (NEB, R0101S) and XhoI (NEB, R0146S) before cloning into a pOptiVEC™-TOPO TA Cloning Kit enclosed in an OptiCHO™ Antibody Express Kit (Cat no. 12762-019, Invitrogen), and a pcDNA™3.3-TOPO TA Cloning Kit (Cat no. 8300-01), respectively.

Each of the constructed vectors was amplified using Qiagen Maxiprep kit (Cat no. 12662), and a transient expression was performed using Freestyle™ MAX 293 Expression System (invitrogen). 293 F cells were used for the expression and cultured in FreeStyle™ 293 Expression Medium in a suspension culture manner. At one day before the transient expression, the cells were provided in the concentration of 5×10⁵ cells/ml, and after 24 hours, when the cell number reached to 1×10⁶ cells/ml, the transient expression was performed. A transfection was performed by a liposomal reagent method using Freestyle™ MAX reagent (invitrogen), wherein in a 15 ml tube, the DNA was provided in the mixture ratio of 1:1 (heavy chain DNA:light chain DNA) and mixed with 2 ml of OptiPro™ SFM (invtrogen) (A), and in another 15 ml tube, 100 ul (microliter) of Freestyle™ MAX reagent and 2 ml of OptiPro™ SFM were mixed (B), followed by mixing (A) and (B) and incubating for 15 minutes. The obtained mixture was slowly mixed with the cells provided one day before the transient expression. After completing the transfection, the cells were incubated in 130 rpm incubator for 5 days under the conditions of 37° C., 80% humidity, and 8% CO₂.

Afterwards, the cells were incubated in DMEM supplemented with 10% (v/v) FBS for 5 hours at 37° C. under a 5% CO₂ condition and then in FBS-free DMEM for 48 hours at 37° C. under a 5% CO₂ condition.

After centrifugation, the supernatant was applied to AKTA prime (GE Healthcare) to purify the antibody. In this regard, 100 mL of the supernatant was loaded at a flow rate of 5 mL/min to AKTA Prime equipped with a Protein A column (GE healthcare, 17-0405-03), followed by elution with an IgG elution buffer (Thermo Scientific, 21004). The buffer was exchanged with PBS to purify a chimeric antibody AbF46 (hereinafter referred to as “chAbF46”).

1.3. Construction of Humanized Antibody huAbF46 from Chimeric Antibody chAbF46

1.3.1. Heavy Chain Humanization

To design two domains H1-heavy and H3-heavy, human germline genes which share the highest identity/homology with the VH gene of the mouse antibody AbF46 purified in Reference Example 1.2 were analyzed. An Ig BLAST (www.ncbi.nlm.nih.gov/igblast/) result revealed that VH3-71 has an identity/identity/homology of 83% at the amino acid level. CDR-H1, CDR-H2, and CDR-H3 of the mouse antibody AbF46 were defined according to Kabat numbering. A design was made to introduce the CDR of the mouse antibody AbF46 into the framework of VH3-71. Hereupon, back mutations to the amino acid sequence of the mouse AbF46 were conducted at positions 30 (S→T), 48 (V→L), 73 (D→N), and 78 (T→L). Then, H1 was further mutated at positions 83 (R→K) and 84 (A→T) to finally establish H1-heavy (SEQ ID NO: 40) and H3-heavy (SEQ ID NO: 41).

For use in designing H4-heavy, human antibody frameworks were analyzed by a BLAST search. The result revealed that the VH3 subtype, known to be most stable, is very similar in framework and sequence to the mouse antibody AbF46. CDR-H1, CDR-H2, and CDR-H3 of the mouse antibody AbF46 were defined according to Kabat numbering and introduced into the VH3 subtype to construct H4-heavy (SEQ ID NO: 42).

1.3.2. Light Chain Humanization

To design two domains H1-light (SEQ ID NO: 43) and H2-light (SEQ ID NO: 44), human germline genes which share the highest identity/homology with the VH gene of the mouse antibody AbF46 were analyzed. An Ig BLAST search result revealed that VK4-1 has a identity/homology of 75% at the amino acid level. CDR-L1, CDR-L2, and CDR-L3 of the mouse antibody AbF46 were defined according to Kabat numbering. A design was made to introduce the CDR of the mouse antibody AbF46 into the framework of VK4-1. Hereupon, back mutations to the amino acid sequence of the mouse AbF46 were conducted at positions 36 (Y→H), 46 (L→M), and 49 (Y→I). Only one back mutation was conducted at position 49 (Y→I) on H2-light.

To design H3-light (SEQ ID NO: 45), human germline genes which share the highest identity/homology with the VL gene of the mouse antibody AbF46 were analyzed by a search for BLAST. As a result, VK2-40 was selected. VL and VK2-40 of the mouse antibody AbF46 were found to have a identity/homology of 61% at an amino acid level. CDR-L1, CDR-L2, and CDR-L3 of the mouse antibody were defined according to Kabat numbering and introduced into the framework of VK4-1. Back mutations were conducted at positions 36 (Y→H), 46 (L→M), and 49 (Y→I) on H3-light.

For use in designing H4-light (SEQ ID NO: 46), human antibody frameworks were analyzed. A Blast search revealed that the Vk1 subtype, known to be the most stable, is very similar in framework and sequence to the mouse antibody AbF46. CDR-L1, CDR-L2, and CDR-L3 of the mouse antibody AbF46 were defined according to Kabat numbering and introduced into the Vk1 subtype. Hereupon, back mutations were conducted at positions 36 (Y→H), 46 (L→M), and 49 (Y→I) on H4-light.

Thereafter, DNA fragments having the heavy chain nucleotide sequences (H1-heavy: SEQ ID NO: 47, H3-heavy: SEQ ID NO: 48, H4-heavy: SEQ ID NO: 49) and DNA fragments having the light chain nucleotide sequences (H1-light: SEQ ID NO: 50, H2-light: SEQ ID NO: 51, H3-light: SEQ ID NO: 52, H4-light: SEQ ID NO: 53) were digested with EcoRI (NEB, R0101S) and XhoI (NEB, R0146S) before cloning into a pOptiVEC™-TOPO TA Cloning Kit enclosed in an OptiCHO™ Antibody Express Kit (Cat no. 12762-019, Invitrogen) and a pcDNA™3.3-TOPO TA Cloning Kit (Cat no. 8300-01), respectively, so as to construct recombinant vectors for expressing a humanized antibody.

Each of the constructed vectors was amplified using Qiagen Maxiprep kit (Cat no. 12662), and a transient expression was performed using Freestyle™ MAX 293 Expression System (invitrogen). 293 F cells were used for the expression and cultured in FreeStyle™ 293 Expression Medium in a suspension culture manner. One day before the transient expression, the cells were provided in the concentration of 5×10⁵ cells/ml, and after 24 hours, when the cell number reached to 1×10⁶ cells/ml, the transient expression was performed. A transfection was performed by a liposomal reagent method using Freestyle™ MAX reagent (invitrogen), wherein in a 15 ml tube, the DNA was provided in the mixture ratio of 1:1 (heavy chain DNA:light chain DNA) and mixed with 2 ml of OptiPro™ SFM (invtrogen) (A), and in another 15 ml tube, 100 ul (microliter) of Freestyle™ MAX reagent and 2 ml of OptiPro™ SFM were mixed (B), followed by mixing (A) and (B) and incubating for 15 minutes. The obtained mixture was slowly mixed with the cells provided one day before the transient expression. After completing the transfection, the cells were incubated in 130 rpm incubator for 5 days under the conditions of 37° C., 80% humidity, and 8% CO₂.

After centrifugation, the supernatant was applied to AKTA prime (GE Healthcare) to purify the antibody. In this regard, 100 mL of the supernatant was loaded at a flow rate of 5 mL/min to AKTA Prime equipped with a Protein A column (GE healthcare, 17-0405-03), followed by elution with an IgG elution buffer (Thermo Scientific, 21004). The buffer was exchanged with PBS to purify a humanized antibody AbF46 (hereinafter referred to as “huAbF46”). The humanized antibody huAbF46 used in the following examples included a combination of H4-heavy (SEQ ID NO: 42) and H4-light (SEQ ID NO: 46).

1.4. Construction of scFV Library of huAbF46 Antibody

For use in constructing an scFv of the huAbF46 antibody from the heavy and light chain variable regions of the huAbF46 antibody, a gene was designed to have the structure of “VH-linker-VL” for each of the heavy and the light chain variable region, with the linker having the amino acid sequence “GLGGLGGGGSGGGGSGGSSGVGS” (SEQ ID NO: 54). A polynucleotide sequence (SEQ ID NO: 55) encoding the designed scFv of huAbF46 was synthesized in Bioneer and an expression vector for the polynucleotide had the nucleotide sequence of SEQ ID NO: 56.

After expression, the product was found to exhibit specificity to c-Met.

1.5. Construction of Library Genes for Affinity Maturation

1.5.1. Selection of Target CDRs and Synthesis of Primers

The affinity maturation of huAbF46 was achieved. First, six complementary determining regions (CDRs) were defined according to Kabat numbering. The CDRs are given in Table 2, below.

TABLE 2 CDR Amino Acid Sequence CDR-H1 DYYMS (SEQ ID NO: 1) CDR-H2 FIRNKANGYTTEYSASVKG(SEQ ID NO: 2) CDR-H3 DNWFAY (SEQ ID NO: 3) CDR-L1 KSSQSLLASGNQNNYLA (SEQ ID NO: 10) CDR-L2 WASTRVS (SEQ ID NO: 11) CDR-L3 QQSYSAPLT (SEQ ID NO: 12)

For use in the introduction of random sequences into the CDRs of the antibody, primers were designed as follows. Conventionally, N codons were utilized to introduce bases at the same ratio (25% A, 25% G, 25% C, 25% T) into desired sites of mutation. In this experiment, the introduction of random bases into the CDRs of huAbF46 was conducted in such a manner that, of the three nucleotides per codon in the wild-type polynucleotide encoding each CDR, the first and second nucleotides conserved over 85% of the entire sequence while the other three nucleotides were introduced at the same percentage (each 5%) and that the same possibility was imparted to the third nucleotide (33% G, 33% C, 33% T).

1.5.2. Construction of a Library of huAbF46 Antibodies and Affinity for c-Met

The construction of antibody gene libraries through the introduction of random sequences was carried out using the primers synthesized in the same manner as in Reference Example 1.5.1. Two PCR products were obtained using a polynucleotide covering the scFV of huAbF46 as a template, and were subjected to overlap extension PCR to give scFv library genes for huAbF46 antibodies in which only desired CDRs were mutated. Libraries targeting each of the six CDRs prepared from the scFV library genes were constructed.

The affinity for c-Met of each library was compared to that of the wildtype. Most libraries were lower in affinity for c-Met, compared to the wild-type. The affinity for c-Met was retained in some mutants.

1.6. Selection of Antibody with Improved Affinity from Libraries

After maturation of the affinity of the constructed libraries for c-Met, the nucleotide sequence of scFv from each clone was analyzed. The nucleotide sequences thus obtained are summarized in Table 3 and were converted into IgG forms. Four antibodies which were respectively produced from clones L3-1, L3-2, L3-3, and L3-5 were used in the subsequent experiments.

TABLE 3 Library Clone constructed CDR Sequence H11-4 CDR-H1 PEYYMS (SEQ ID NO: 22) YC151 CDR-H1 PDYYMS (SEQ ID NO: 23) YC193 CDR-H1 SDYYMS (SEQ ID NO: 24) YC244 CDR-H2 RNNANGNT (SEQ ID NO: 25) YC321 CDR-H2 RNKVNGYT (SEQ ID NO: 26) YC354 CDR-H3 DNWLSY (SEQ ID NO: 27) YC374 CDR-H3 DNWLTY (SEQ ID NO: 28) L1-1 CDR-L1 KSSHSLLASGNQNNYLA (SEQ ID NO: 29) L1-3 CDR-L1 KSSRSLLSSGNHKNYLA (SEQ ID NO: 30) L1-4 CDR-L1 KSSKSLLASGNQNNYLA (SEQ ID NO: 31) L1-12 CDR-L1 KSSRSLLASGNQNNYLA (SEQ ID NO: 32) L1-22 CDR-L1 KSSHSLLASGNQNNYLA (SEQ ID NO: 33) L2-9 CDR-L2 WASKRVS (SEQ ID NO: 34) L2-12 CDR-L2 WGSTRVS (SEQ ID NO: 35) L2-16 CDR-L2 WGSTRVP (SEQ ID NO: 36) L3-1 CDR-L3 QQSYSRPYT (SEQ ID NO: 13) L3-2 CDR-L3 GQSYSRPLT (SEQ ID NO: 14) L3-3 CDR-L3 AQSYSHPFS (SEQ ID NO: 15) L3-5 CDR-L3 QQSYSRPFT (SEQ ID NO: 16) L3-32 CDR-L3 QQSYSKPFT (SEQ ID NO: 37)

1.7. Conversion of Selected Antibodies into IgG

Respective polynucleotides encoding heavy chains of the four selected antibodies were designed to have the structure of “EcoRI-signal sequence-VH-NheI-CH-XhoI” (SEQ ID NO: 38). The heavy chains of huAbF46 antibodies were used as they were because their amino acids were not changed during affinity maturation. In the case of the hinge region, however, the U6-HC7 hinge (SEQ ID NO: 57) was employed instead of the hinge of human IgG1. Genes were also designed to have the structure of “EcoRI-signal sequence-VL-BsiWI-CL-XhoI” for the light chain. Polypeptides encoding light chain variable regions of the four antibodies which were selected after the affinity maturation were synthesized in Bioneer. Then, a DNA fragment having the heavy chain nucleotide sequence (SEQ ID NO: 38) and DNA fragments having the light chain nucleotide sequences (DNA fragment including L3-1-derived CDR-L3: SEQ ID NO: 58, DNA fragment including L3-2-derived CDR-L3: SEQ ID NO: 59, DNA fragment including L3-3-derived CDR-L3: SEQ ID NO: 60, and DNA fragment including L3-5-derived CDR-L3: SEQ ID NO: 61) were digested with EcoRI (NEB, R0101S) and XhoI (NEB, R0146S) before cloning into a pOptiVEC™-TOPO TA Cloning Kit enclosed in an OptiCHO™ Antibody Express Kit (Cat no. 12762-019, Invitrogen) and a pcDNA™3.3-TOPO TA Cloning Kit (Cat no. 8300-01), respectively, so as to construct recombinant vectors for expressing affinity-matured antibodies.

Each of the constructed vectors was amplified using Qiagen Maxiprep kit (Cat no. 12662), and a transient expression was performed using Freestyle™ MAX 293 Expression System (invitrogen). 293 F cells were used for the expression and cultured in FreeStyle™ 293 Expression Medium in a suspension culture manner. At one day before the transient expression, the cells were provided in the concentration of 5×10⁵ cells/ml, and after 24 hours, when the cell number reached to 1×10⁶ cells/ml, the transient expression was performed. A transfection was performed by a liposomal reagent method using Freestyle™ MAX reagent (invitrogen), wherein in a 15 ml tube, the DNA was provided in the mixture ratio of 1:1 (heavy chain DNA:light chain DNA) and mixed with 2 ml of OptiPro™ SFM (invtrogen) (A), and in another 15 ml tube, 100 ul (microliter) of Freestyle™ MAX reagent and 2 ml of OptiPro™ SFM were mixed (B), followed by mixing (A) and (B) and incubating for 15 minutes. The obtained mixture was slowly mixed with the cells provided one day before the transient expression. After completing the transfection, the cells were incubated in 130 rpm incubator for 5 days under the conditions of 37° C., 80% humidity, and 8% CO₂.

After centrifugation, the supernatant was applied to AKTA prime (GE Healthcare) to purify the antibody. In this regard, 100 mL of the supernatant was loaded at a flow rate of 5 mL/min to AKTA Prime equipped with a Protein A column (GE healthcare, 17-0405-03), followed by elution with an IgG elution buffer (Thermo Scientific, 21004). The buffer was exchanged with PBS to purify four affinity-matured antibodies (hereinafter referred to as “huAbF46-H4-A1 (L3-1 origin), huAbF46-H4-A2 (L3-2 origin), huAbF46-H4-A3 (L3-3 origin), and huAbF46-H4-A5 (L3-5 origin),” respectively).

1.8. Construction of Constant Region- and/or Hinge Region-Substituted huAbF46-H4-A1

Among the four antibodies selected in Reference Example 1.7, huAbF46-H4-A1 was found to be the highest in affinity for c-Met and the lowest in Akt phosphorylation and c-Met degradation degree. In the antibody, the hinge region, or the constant region and the hinge region, were substituted.

The antibody huAbF46-H4-A1 (U6-HC7) was composed of a heavy chain including the heavy chain variable region of huAbF46-H4-A1, U6-HC7 hinge, and the constant region of human IgG1 constant region, and a light chain including the light chain variable region of huAbF46-H4-A1 and human kappa constant region. The antibody huAbF46-H4-A1 (IgG2 hinge) was composed of a heavy chain including a heavy chain variable region, a human IgG2 hinge region, and a human IgG1 constant region, and a light chain including the light chain variable region of huAbF46-H4-A1 and a human kappa constant region. The antibody huAbF46-H4-A1 (IgG2 Fc) was composed of the heavy chain variable region of huAbF46-H4-A1, a human IgG2 hinge region, and a human IgG2 constant region, and a light chain including the light variable region of huAbF46-H4-A1 and a human kappa constant region. Hereupon, the histidine residue at position 36 on the human kappa constant region of the light chain was changed to tyrosine in all of the three antibodies to increase antibody production.

For use in constructing the three antibodies, a polynucleotide (SEQ ID NO: 63) encoding a polypeptide (SEQ ID NO: 62) composed of the heavy chain variable region of huAbF46-H4-A1, a U6-HC7 hinge region, and a human IgG1 constant region, a polynucleotide (SEQ ID NO: 65) encoding a polypeptide (SEQ ID NO: 64) composed of the heavy chain variable region of huAbF46-H4-A1, a human IgG2 hinge region, and a human IgG1 region, a polynucleotide (SEQ ID NO: 67) encoding a polypeptide (SEQ ID NO: 66) composed of the heavy chain variable region of huAbF46-H4-A1, a human IgG2 region, and a human IgG2 constant region, and a polynucleotide (SEQ ID NO: 69) encoding a polypeptide (SEQ ID NO: 68) composed of the light chain variable region of huAbF46-H4-A1, with a tyrosine residue instead of histidine at position 36, and a human kappa constant region were synthesized in Bioneer. Then, the DNA fragments having heavy chain nucleotide sequences were inserted into a pOptiVEC™-TOPO TA Cloning Kit enclosed in an OptiCHO™ Antibody Express Kit (Cat no. 12762-019, Invitrogen) while DNA fragments having light chain nucleotide sequences were inserted into a pcDNA™3.3-TOPO TA Cloning Kit (Cat no. 8300-01) so as to construct vectors for expressing the antibodies.

Each of the constructed vectors was amplified using Qiagen Maxiprep kit (Cat no. 12662), and a transient expression was performed using Freestyle™ MAX 293 Expression System (invitrogen). 293 F cells were used for the expression and cultured in FreeStyle™ 293 Expression Medium in a suspension culture manner. At one day before the transient expression, the cells were provided in the concentration of 5×10⁵ cells/ml, and after 24 hours, when the cell number reached to 1×10⁶ cells/ml, the transient expression was performed. A transfection was performed by a liposomal reagent method using Freestyle™ MAX reagent (invitrogen), wherein in a 15 ml tube, the DNA was provided in the mixture ratio of 1:1 (heavy chain DNA:light chain DNA) and mixed with 2 ml of OptiPro™ SFM (invtrogen) (A), and in another 15 ml tube, 100 ul (microliter) of Freestyle™ MAX reagent and 2 ml of OptiPro™ SFM were mixed (B), followed by mixing (A) and (B) and incubating for 15 minutes. The obtained mixture was slowly mixed with the cells provided one day before the transient expression. After completing the transfection, the cells were incubated in 130 rpm incubator for 5 days under the conditions of 37° C., 80% humidity, and 8% CO₂.

After centrifugation, the supernatant was applied to AKTA prime (GE Healthcare) to purify the antibody. In this regard, 100 mL of the supernatant was loaded at a flow rate of 5 mL/min to AKTA Prime equipped with a Protein A column (GE healthcare, 17-0405-03), followed by elution with IgG elution buffer (Thermo Scientific, 21004). The buffer was exchanged with PBS to finally purify three antibodies (huAbF46-H4-A1 (U6-HC7), huAbF46-H4-A1 (IgG2 hinge), and huAbF46-H4-A1 (IgG2 Fc)). Among the three antibodies, huAbF46-H4-A1 (IgG2 Fc) was representatively selected for the following examples, and referred as anti-c-Met antibody L3-1Y-IgG2.

Example 1 Preparation of a PEGylated Antibody

Methoxypolyethyleneglycol (mPEG; molecular weight: 10, 20, or 30 kDa) was added to the prepared antibody L3-1Y/IgG2 (50 mM) at the amount of 0 to 350 mM, to conduct a PEGylation reaction (reaction conditions: 40 mM NaCNBH₃, pH 5.0, 4° C., 48 hours; see FIG. 1).

To confirm of formation of an antibody having PEG at N-terminus thereof, a SDS-PAGE analysis (NuPAGE™ SDS-PAGE gel system, Thermo Fisher Scientific Inc.) was performed. The obtained results are demonstrated in FIG. 2. As shown in FIG. 2, it is confirmed that an antibody where PEG is introduced at N-terminus of a heavy chain (N_(HC) PEGylation) or N-terminus of a light chain (N_(LC) PEGylation) is formed.

Example 2 Optimization of a PEGylation Reaction

An antibody and a polyethyleneglycol were reacted at various feed ratios, to deduce an optimal reaction ratio for obtaining an optimal mono-PEGylation.

Referring to the description of Example 1, PEG-introduced antibodies were prepared by reacting a polyethyleneglycol (molecular weight: 20 kDa) and an antibody L3-1Y/IgG2 (50 mM) at various molar ratios (mole of PEG/mole of antibody: 0, 1, 2, 3, 4, 5, 6, or 7). Reaction conditions were otherwise as described in Example 1.

The prepared PEG-introduced antibody was subjected to an IEX-HPLC analysis (Ion exchange-HPLC; using Alliance HPLC instrument (Water) and MonoS column (GE Healthcare)). The obtained results are demonstrated in FIG. 3. In addition, from the HPLC results, the fractions (%) of unreacted antibody (Unreacted Ab), Mono PEG Ab (wherein one PEG is conjugated to one antibody), and Multi PEG Ab (wherein several (at least two) PEGs are conjugated to one antibody) according to reaction molar ratios between an antibody and PEG were quantitated, and demonstrated in FIG. 4.

As shown in FIGS. 3 and 4, when the molar ratio between an antibody and PEG (PEG/antibody) is about 3 or more, “Mono PEG Ab” (wherein one PEG is conjugated to one antibody) is obtained at relatively high yield; and when the molar ratio between an antibody and PEG (PEG/antibody) is about 7 or more, the increase in the yield of “Mono PEG Ab” slows down. Therefore, the optimal molar ratio between an antibody and PEG (PEG/antibody) for producing “Mono PEG Ab” can be determined as about 3 to about 7.

In addition, the obtained reaction mixture, unreacted antibodies, Mono PEG Ab and Multi-PEG Ab were analyzed through SEC-HPLC and IEX-HPLC. The SEC-HPLC was performed using Alliance HPLC instrument (Waters), TSKgel G3000SW column (Tosoh), and a buffer (PBS; pH 7.4), and the IEX-HPLC was performed using Alliance HPLC instrument (Waters), MonoS column (GE Healthcare), and a buffer (20 mM acetate buffer; pH 5.0).

The obtained results are demonstrated in FIG. 9 (SEC-HPLC) and FIG. 10 (IEX-HPLC). As shown in FIGS. 9 and 10, “Mono-PEG Ab” with high purity (about 95% or more) can be obtained by the above process.

Example 3 Preparation and Analysis of PEG-Ab Having PEG with Various Molecular Weights

Referring to the description of Example 1, polyethyleneglycol with the molecular weight of 30 kDa, 20 kDa, or 10 kDa was reacted with an antibody L3-1Y/IgG2 (50 mM) at the molar ratio (PEG/antibody) of 5, to PEG-introduced antibodies containing PEG with various molecular weights. Reaction conditions were otherwise as described in Example 1.

It was confirmed by HPLC that the obtained products are PEG-introduced antibodies wherein PEG with various molecular weights is introduced at N-terminus of an antibody. The HPLC results are demonstrated in FIG. 5.

To confirm whether the prepared PEG-introduced antibodies containing PEG with various molecular weights can maintain the binding affinity to the antigen, the binding affinity of the prepared PEG-introduced antibodies to c-Met was measured using Biacore T100(GE) and compared with that of an antibody with no PEG (Ab).

In particular, human Fab binder (GE Healthcare) was fixed on a surface of CM5 chip (#BR-1005-30, GE) according to the manufacturer's manual. About 90 to 120 Ru of each of the PEG-introduced antibodies was captured, and c-Met-Fc (#358-MT/CF, R&D Systems) was injected at various concentrations into the captured PEG-introduced antibody. 10 mM Glycine-HCl (pH 1.5) solution was injected thereto to regenerate the surface. In order to measure affinity, the data obtained from this experiment was fitted using BIAevaluation software (GE Healthcare, Biacore T100 evaluation software).

The measured affinities to c-Met are summarized in Table 4.

TABLE 4 Sample Ka (*10⁵, 1/s) Kd (*10⁻⁵, 1/MS) KD (pM) Chi² Ab 9.287 7.644 82.31 0.393 10kPEG Ab 11.75 10.03 85.95 1.38 20kPEG Ab 9.989 7.281 72.89 1.40 30kPEG Ab 14.30 8.858 61.95 1.39

As shown in Table 4, the PEG-introduced antibodies maintain the affinity to the antigen (c-Met) at the similar level to that of an antibody with no PEG (Ab), and the affinity is generally higher as the molecular weight of PEG is larger.

Example 4 Bioactivity Analysis of PEG-Ab Having PEG with Various Molecular Weights

It was examined whether the PEG-introduced antibodies containing PEG with various molecular weights prepared in Example 3 maintain their bioactivities (e.g., a cytotoxicity to a cancer cell) after N-terminal PEGylation. For this, the cytotoxicity of the prepared PEG-introduced antibodies was examined to a c-Met positive cancer cell line NKN45.

In particular, MKN45 gastric cancer cells (JCRB0254, JCRB Cell Bank, Japan) were seeded in 96-well(BD) at the amount of 10×10³ cells per each well, and 24 hours after, each of mono-PEG antibody (wherein PEG with the molecular weight of 10, 20, or 30 kDa is conjugated to L3-1Y/IgG2) and L3-1Y/IgG2 with no PEG, which is mixed with a medium, was added thereto so that the final concentration of the antibody reaches experimental concentrations (0 to 100 nM; see FIG. 6). 72 hours after the antibody treatment, 10 uL of CCK-8 reagent (CK04, Dojindo) was added to each well, and left in 37° C. incubator for 2 hours and 30 minutes, and then, absorbance at dual wavelengths (450 and 650 nm) was read by a micro-plate reader (Molecular Device).

The obtained results are demonstrated in FIG. 6. As shown in FIG. 6, the PEG-introduced antibodies containing PEG with various molecular weights exhibits the similar level of cell growth inhibition effect to that of the anti-c-Met antibody L3-1Y/IgG2 with no PEG.

Example 5 Examination of Decreased Aggregation of an Antibody-Drug Conjugate (ADC)

It was examined whether the aggregation is decreased when the PEG-introduced antibody is conjugated with a drug.

In particular, L3-1Y/IgG2 (Reference Example) or the PEG-introduced antibody (Example 1; molecular weight of PEG: 20 kDa; mono-PEG; molar ratio (PEG/antibody): 5) and a hydrophobic drug, doxorubicin (Sigma-Aldrich) were mixed so that the molar ratio (DAR; drug-to-antibody ratio; mole of drug/mole of antibody) is 5, 10 or 15, to produce an antibody-drug conjugate (PEG ADC).

The obtained products were subjected to a HPLC analysis, and the obtained results are demonstrated in FIG. 7. In FIG. 7, peaks within boxes signify ADC monomer or PEG-ADC monomer, and the other peaks that are not within the boxes signify impurities generated by aggregation. As shown in FIG. 7, compared to the case using an antibody with no PEG, in the case using the PEG-introduced antibody, the rate of production of PEG ADC monomer is higher and the aggregation is decreased. In addition, when the molar ratio of an antibody and a drug is 5, the rate of production of PEG ADC monomer is superior.

Example 6 Examination of Improved In Vivo PK Profile

The in vivo pharmacokinetic profiles of a conjugate of the PEG-introduced antibody and a drug were examined.

The conjugate (mole of drug/mole of antibody: 5) of the mono-PEG antibody and doxorubicin prepared in Example 5 was intravenously administered to a SD (Sprague Dawley) rat (the body weight: 200 g) at the amount of 3 mg/kg. About 500 μL of blood was sampled from a jugular vein of the rat at each of 10 minutes, 30 minutes, 1 hour, 3 hours, 6 hours, 9 hours, 12 hours, 24 hours, 36 hours, 48 hours, 72 hours, and 120 hours after the administration. The obtained blood sample was centrifuged to obtain a separated blood plasma. The concentrations of the antibody-drug conjugate (ADC) and mono-PEG-introduced antibody-drug conjugate (PEG-ADC) in the separated blood plasma were measured by ELISA assay. The obtained results are demonstrated in FIG. 8. In addition, the parameters of pharmacokinetic profiles were analyzed using Non-Compartment Model, and the results are summarized in Table 5.

TABLE 5 Parameters Units ADC PEG-ADC ‘AUC’(area under the curve) μg*h/mL 2601.2 4426.9 ‘CL’(clearance) mL/h/kg 0.38444 0.2589 ‘MRT’(mean residence time) h 105.47 275.32 ‘T_half’(half-life) h 82.706 203.31 ‘V_ss’ (volume of distribution) mL/kg 40.549 58.937

In Table 5 and FIG. 8, “ADC” refers to the antibody (with no PEG)-drug conjugate and “PEG ADC” refers to the mono-PEG-introduced antibody-drug conjugate.

As shown in Table 5, compared to the antibody (with no PEG)-drug conjugate, the mono-PEG-introduced antibody-drug conjugate exhibits generally improved pharmacokinetic profiles.

It should be understood that the exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments.

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

The use of the terms “a” and “an” and “the” and “at least one” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term “at least one” followed by a list of one or more items (for example, “at least one of A and B”) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. 

What is claimed is:
 1. A polyethylene glycol (PEG)-modified targeting compound, comprising a polyethyleneglycol molecule bound to a targeting compound, wherein the polyethyleneglycol molecule has a molecular weight of 1,000 to 100,000 Da, and the targeting compound is an antibody, an antigen-binding antibody fragment-Fc conjugate, a protein scaffold, or a protein scaffold-Fc conjugate.
 2. The PEG-modified targeting compound of claim 1, wherein the antibody is an IgG1, IgG2, IgG3, or IgG4 antibody, and the antigen-binding antibody fragment-Fc conjugate is an scFvFc fragment.
 3. The PEG-modified targeting compound of claim 1, wherein the polyethyleneglycol molecule has a molecular weight of 10,000 to 100,000 Da.
 4. The PEG-modified targeting compound of claim 1, wherein the polyethyleneglycol molecule is bound to the N-terminus of the targeting compound, or bound to a free cysteine or a free thiol group on the targeting compound.
 5. A pharmaceutical composition for drug delivery comprising the PEG-modified targeting compound of claim 1 and a pharmaceutically acceptable carrier, diluent, or excipient.
 6. An antibody-drug conjugate comprising a polyethylene glycol (PEG)-modified antibody and a drug.
 7. The antibody-drug conjugate of claim 6, wherein the drug is a hydrophobic drug.
 8. The antibody-drug conjugate of claim 6, wherein the antibody is an immunoglobulin antibody or an antigen-binding antibody fragment-Fc conjugate.
 9. The antibody-drug conjugate of claim 6, wherein the polyethyleneglycol has the molecular weight of 1,000 to 100,000 Da.
 10. The antibody-drug conjugate of claim 6, wherein the polyethyleneglycol is bound to the N-terminus of the antibody, or bound to a free cysteine or a free thiol group of the antibody.
 11. A method of preparing an antibody-drug conjugate comprising combining a polyethyleneglycol (PEG)-modified antibody and a drug to form an antibody-drug conjugate.
 12. A method for drug delivery comprising administering the antibody-drug conjugate of claim 6 to a subject.
 13. The method for drug delivery of claim 12, wherein the drug is a hydrophobic drug.
 14. The method for drug delivery of claim 12, wherein the antibody is an immunoglobulin antibody or an antigen-binding antibody fragment-Fc conjugate.
 15. The method for drug delivery of claim 12, wherein the polyethyleneglycol has a molecular weight of 1,000 to 100,000 Da.
 16. The method for drug delivery of claim 12, wherein the polyethyleneglycol is bound to the N-terminus of the antibody, or bound to a free cysteine or a free thiol group of the antibody.
 17. A pharmaceutical composition comprising the antibody-drug conjugate of claim 6 and a pharmaceutically acceptable carrier, diluent, or excipient.
 18. A method of preparing a PEG-modified antibody comprising combining an antibody with PEG at a PEG:antibody molar ratio of about 3 to about
 7. 19. The PEG-modified targeting compound of claim 1, wherein the targeting compound is an antibody, and the antibody comprises a single PEG molecule bound to the N-terminus of the heavy or light chain of the antibody.
 20. The PEG-modified targeting compound of claim 19, wherein the PEG molecule has a molecular weight of 10,000 to 100,000 Da. 